PROJECT SUMMARY Human noroviruses (HuNoVs) are a leading causes of gastroenteritis in the United States and globally. The significant public health burden associated with this pathogen has stimulated efforts in vaccine development and in the evaluation of antivirals. However, a number of fundamentally important questions on virus pathogenesis and protective immune responses remain unanswered and addressing these challenges is critical for the development of effective strategies to prevent and treat HuNoV infections. In this project, we aim to: (i) Elucidate factors that mediate clinical presentations associated with HuNoV gastroenteritis; (ii) Develop and pre-clinically test drug-like inhibitors of virus protease and polymerase as potential antiviral agents; and (iii) Determine HuNoV epitopes recognized by the human immune system during infection and identify epitopes associated with virus neutralization and protective immunity. Using clinical data and samples from previous human experimental challenge studies, together with infectivity assays in human intestinal enteroids (HIEs) allows us to carry out functional and mechanistic on HuNoV pathogenesis and virus neutralization. The HIE cultivation system also, for the first time, allows us to directly evaluate antivirals. The findings from this project will therefore provide new understanding of the mechanisms of HuNoV disease and identify potential targets that can used to treat disease symptoms. Drug-like inhibitors prioritized through rational drug design and medicinal chemistry will be evaluated for their effects on inhibition of virus and key factors associated with infection and disease. Finally, identification of antibody repertoires that correlate with protective immunity and virus neutralization will inform vaccine design and testing. Together, these studies will enable functional, mechanistic and translational contributions that will reduce the public health burden of HuNoV gastroenteritis. .